Researchers Develop Chlorine-Tolerant Membrane for Easy Desalination

Record droughts, falling water tables and the rapid depletion of aquifers have helped make desalination, a process once considered impractical and too expensive, a viable technology -- at least in some places. As such, there has been a rash of stories -- both here and elsewhere in the blogosphere/traditional media (The Economist featured an excellent special report a few weeks ago) -- in recent months dealing with the construction of new desalination facilities and the unveiling of innovative membrane technologies.

A team of researchers from the University of Texas at Austin and Virginia Tech University has developed a chlorine-tolerant membrane that could simplify desalination and bring it within the reach of many drought-stricken regions. Chlorine-tolerant membrane would improve the performance, lower the costs of desalinationDe-chlorination is typically one of the most costly, time consuming steps in the desalination process. Chlorine is added to seawater to disinfect it and to prevent the formation of a biofilm, a polymer-like coat of microorganisms that lowers the membrane's efficiency. However, because chlorine is damaging to the polyamide membranes that are currently in use, an extra de-chlorination step is required before the treated water can be filtered. Polyamide membranes that are repeatedly exposed to aqueous chlorine degrade over time and lose their effectiveness.

A lower carbon footprintThe membrane developed by the scientists, which is made of sulfonated copolymers, can withstand chlorine and therefore loses none of its potency, even after repeated exposure. Benny Freeman, a professor at UT-Austin and one of the leading scientists on this project, believes the membrane will not only help improve the performance of desalination (and make it much cheaper) but also reduce its carbon footprint:

"Energy and water are inherently connected. You need water to generate power (cooling water for electric power generation stations) and generation of pure water requires energy to separate the salt from the water. That energy is often generated from the burning of fossil fuels, which leads inevitably to the generation of carbon dioxide. Therefore, if one can make desalination more energy-efficient by developing better membranes, such as those that we are working on, one could reduce the carbon footprint required to produce pure water."

The results of their work was published in the July 28 issue of Angewandte Chemie. Freeman and his colleagues have filed a patent for the technology.

Though desalination remains prohibitively expensive, technologies such as this could help ease its introduction in other parched regions of the world. Many of the other technologies we've reported on in the past (see link list below and our archive) will also have an impact. In the short-term, a more effective solution to our water woes would simply be to put a price on water that accurately reflected the laws of supply and demand, an argument made more forcefully (and eloquently) by David Zetland, proprietor of Aguanomics.